Bradford 69.
OK, so your question is perhaps expressed as "WTF is a Variance?"
This is a poor definition, but here goes:
There is a legal difference between the many variations of "Demostration Laser Products", used in public or private events. Laser shows are a special set of the rules that are not well defined by Congress.
Many things are what used to be/may still be called a "Demonstration Laser Product". A laser gun sight, or a HENE made for a high school physics lab, or a low power laser used for leveling pipes on a construction site are examples. The demonstration laser greater then 4.95 mW in some cases, or .9 mW in others, needs manufacturing documents and a variance for its use.
A variance is legal permission on a case by case basis to deviate from the safety rules that would otherwise restrict laser shows to harmless Class II or Class IIIA low power lasers. Harmless in this case means highly unlikely to cause eye damage.
Many devices, not laser shows, just need the manufacturing documents and a quality control program. Laser show devices need a QC program, Manufacturing Approval, and a Variance for use.
The IIIA product, like a gun sight, is created under a different subset of the rules after the manufacturer documents that it meets certain requirements that make it a low power, and essentially harmless laser device. They are required to show quality control measures on their devices.
Pointers less then 5mW have a blanket permission to manufacture now under one of the "Laser Letters" issued by FDA, provided they are less then 4.95 mW when sampled, and have certain stickers on them. This was done to reduce paperwork load on both sides. It has then been abused as powers have gotten higher.
Other laser products such as laser welders are supposed to built in such a way that you cannot be exposed power in excess of class I, ie 300 microwatts, by encasing the beam path or other techniques such as interlock switches.
Medical lasers are supposed to be used only by trained medical staff.
Lab Lasers are expected to be used in a compliant manner described by ANSI Z136, ie access is restricted to lab personnel, and other measures should be taken.
This is a short summary typed at 5 Am, it has multiple errors.
I hope that helps.
Steve